The thermal diffusivity of y-alumina is determined by the photoacoustic method. The method is
calibrated by determining the thermal diffusivity of copper and aluminum. The effect of the
chemisorbed hydroxyl groups or thermal diffusivity is studied by degassing the sample at different
temperatures.

Analysis of the emission bands of the CN molecules in the plasma generated from
a graphite target irradiated with 1-06/~m radiation pulses from a Q-switched Nd:YAG laser has
been done. Depending on the position of the sampled volume of the plasma plume, the intensity
distribution in the emission spectra is found to change drastically. The vibrational temperature
and population distribution in the different vibrational levels have been studied as function of
distance from the target for different time delays with respect to the incidence of the laser pulse.
The translational temperature calculated from time of flight is found to be higher than the
observed vibrational temperature for CN molecules and the reason for this is explained.

We propose to show in this paper, that the time series obtained from biological systems such as human brain are invariably nonstationary because of different time scales involved in the dynamical process. This makes the invariant parameters time dependent. We made a global analysis of the EEG data obtained from the eight locations on the skull space and studied simultaneously the dynamical characteristics from various parts of the brain. We have proved that the dynamical parameters are sensitive to the time scales and hence in the study of brain one must identify all relevant time scales involved in the process to get an insight in the working of brain.

Files in this item: 1

A simple technique to improve the impedance bandwidth of a circular
microstrip patch antenna using two sectorial slots is proposed. Using this
design more than 5% impedance bandwidth is obtained. The added
advantage of this new antenna is that it can be fed by a 50 microstrip
line

Files in this item: 1

A simple technique to improve the impedance bandwidth of a circular
microstrip patch antenna using two sectorial slots is proposed. Using this
design more than 5% impedance bandwidth is obtained. The added
advantage of this new antenna is that it can be fed by a 50microstrip
line

Files in this item: 1

Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate , periodically
loaded with thin conducting strips . The antenna is found
to be simulating the radiation characteristics of metallic corrugated
horns . This can be an ideal substitute for metallic corrugated
horns with added advantages like light -weight and low
production cost.

Files in this item: 1

Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate , periodically
loaded with thin conducting strips . The antenna is found
to be simulating the radiation characteristics of metallic corrugated
horns . This can be an ideal substitute for metallic corrugated
horns with added advantages like light -weight and low
production cost.

Optical emission studies of C2 molecules in plasma obtained by Nd:YAG
laser ablation of graphite in a helium atmosphere are reported for irradiances in the
range (1–9:2/ x 1010 W cm−2. The characteristics of the spectral emission intensity
from the C2 (Swan band) species have been investigated as functions of the
distance from the target, ambient pressure and laser irradiance. Estimates of
vibrational temperatures of C2 species under various irradiance conditions are
made. Results of measurements performed under different ambient helium gas
pressures are also discussed.

D.C. and a.c. electrical conductivities, dielectric constant and dielectric loss factor in single crystals of ethylenediammonium sulphate, (H3NCH2CH2NH3)(SO4), have been measured axiswise as a function of temperature. Anomalous variations in all the above properties at 480 K indicate the occurrence of a phase transition in the above material at this temperature. The existence of such a phase transition is also confirmed by DSC measurements. Electrical conductivity results are analysed and the activation energies of conduction at different temperature regions have been evaluated from the logσ vs 103T−1 plot. Possible mechanisms for the electrical conduction process are discussed, the available results being in favour of a proton transport model.

A laser produced plasma from the multielement solid target YBa2Cu3O7 is generated using 1.06 μm, 9 ns pulses from a Q-switched Nd:YAG laser in air at atmospheric pressure. A time resolved analysis of the profile of the 4554.03 Å resonance line emission from Ba II at various laser power densities has been carried out. It has been found that the line has a profile which is strongly self-reversed. It is also observed that at laser power densities equal to or exceeding 1.6×1011 W cm−2, a third peak begins to develop at the centre of the self-reversed profile and this has been interpreted as due to the anisotropic resonance scattering (fluorescence). The number densities of singly ionized barium ions evaluated from the width of the resonance line as a function of time delay with respect to the beginning of the laser pulse give typical values of the order of 1019 cm−3. The higher ion concentrations existing at smaller time delays are seen to decrease rapidly. The Ba II ions in the ground state resonantly absorb the radiation and this absorption is maximum around 120 ns after the laser pulse.